When using a service on the web, a bank service, or the like by using a mobile terminal or an ATM (Automatic Teller Machine), password authentication for identification is performed. The password authentication requires measures against password leakage due to shoulder surfing, secret photography, and the like at the scene of an input operation of a password.
Various techniques for preventing password leakage due to shoulder surfing and secret photography have been known. As one of such techniques, Patent Literature 1 discloses the following. A hiragana table capable of selectively inputting characters is displayed on an authentication terminal (ATM main body). Meanwhile, a correspondence table for associating characters with numerals is transmitted from the authentication terminal to the user's mobile terminal. The user enters a character string corresponding to a password (numeric string) into the authentication terminal by referring to the correspondence table on the mobile terminal. This can reduce the risk of the occurrence of password leakage as compared to a method for directly entering the password.
In Patent Literature 2, a plurality of button images to which numerical values of 0 to 9 are assigned at random are displayed on a display of a TV set. The plurality of button images are displayed in the same layout as that of a plurality of numeric keys of a remote controller to which numerals of 0 to 9 are assigned in a fixed manner. Instead of entering numerical values of a password itself from the remote controller, the user checks the positions of the button images to which the respective numerical values constituting the user's password are assigned on the arrangement of the plurality of button images displayed on the display of the TV set, and operates the numeric keys of the remote controller lying in the same positions. This is said to be able to prevent leakage of the password occurring because the plurality of numeric keys operated on the remote controller and the order of operation are visually observed by a third party.